We wish to determine whether it is possible to protect animals against carcinogenesis induced by certain classes of chemicals, such as polycyclic aromatic hydrocarbon (PAH) carcinogens, by immunizing them with non-carcinogenic analogs. Mice will be immunized with 5-fluoro-12-methylbenzanthryl-7-acetic acid (FMBAAA) conjugated to bovine serum albumin (BSA), or with other non-carcinogenic PAH's. They will then be exposed to the carcinogenic PAH's, dimethylbenzanthracene or benzopyrene, to determine whether they are protected against the local induction of skin tumors. Similar potection experiments will be performed, if feasible, to determine the effects of respiratory tract immunization on tumor incidence and on histological changes induced by benzopyrene in the respiratory tract.